Sutures are commonly used for closing or binding together wounds in human or animal tissue, such as skin, muscles, tendons, internal organs, nerves, and blood vessels. Sutures can be formed from non-absorbable material such as silk, nylon, polypropylene, or cotton, or alternatively sutures can be formed from bio-absorbable material such as, but not limited to, homopolymers and/or copolymers of glycolide, lactide, p-dioxanone and ε-caprolactone.
A suture can include retainers protruding from the suture periphery. These retainers are arranged to allow passage of the self-retaining suture when drawn in one direction (with respect to the direction of protrusion of the retainer) through tissue. Such retainers, however, resist movement when the self-retaining suture is drawn in the opposite direction. Self-retaining sutures can reduce slippage of the suture and can optionally obviate knotting of the suture.
Sutures typically consist of a filamentous suture thread with a needle with a sharp point (attachment of sutures and surgical needles is described in U.S. Pat. Nos. 3,981,307, 5,084,063, 5,102,418, 5,123,911, 5,500,991, 5,722,991, 6,012,216, and 6,163,948, and U.S. Patent Application Publication No. 2004/0088003).
Self-retaining sutures (often referred to as “self-retaining sutures”) differ from conventional sutures in that they possess numerous tiny retainers (often barbs) which anchor into the surrounding tissue following deployment, thereby eliminating the need to tie knots to affix adjacent tissues together, and have been described in, for example, U.S. Pat. No. 6,848,152 and European Patent 1 075 843. Such retainers protrude from the suture periphery and are arranged to allow passage of the self-retaining suture when drawn in one direction (with respect to the direction of protrusion of the retainer) through tissue but resist movement of the self-retaining suture when drawn in the opposite direction. Retainers can reduce slippage of the suture at least in a direction along the suture and can optionally obviate knotting of the suture.
A self-retaining suture may be unidirectional, having one or more retainers oriented in one direction along the length of the suture thread; or bidirectional, typically having one or more retainers oriented in one direction along a portion of the thread, followed by one or more retainers oriented in another (often opposite) direction over the remainder of the thread (as described in the context of barbed retainers in U.S. Pat. Nos. 5,931,855 and 6,241,747). Although any number of sequential or intermittent configurations of retainers are possible, the most common form involves a needle at one end, followed by barbs projecting “away” from the needle until the transition point (often the midpoint) of the suture is reached; at the transition point the configuration of barbs reverses itself 180° (i.e., the barbs are now facing in the opposite direction) along the remaining length of the suture thread before attaching to a second needle at the opposite end. The disclosures of all patents and patent applications mentioned herein are incorporated by reference.
Single-directional self-retaining sutures can include an end that is pointed or has a needle to allow penetration and passage through tissue when drawn by the end and, if desired, an opposite end that includes an anchor for engaging tissue at the initial insertion point to limit movement of the suture. Alternatively, bi-directional self-retaining sutures can include retainers grouped and extending in one direction along one portion of the suture and opposing retainers grouped and extending in an opposing direction along another portion of the suture. When implanted, so that both groups of retainers are engaging tissue, the retainers can resist movement of the suture through tissue in either direction.
A surgeon may use a surgical needle with an attached suture to pierce the tissue alternately on opposing faces of a wound to sew the wound closed. Techniques for placement of self-retaining sutures in tissue to close or bind together wounds can include threading the self-retaining suture in straight-line patterns such as a zig-zag pattern as well as threading the suture in curvilinear patterns such as alpha, sinusoidal, and corkscrew patterns. A surgeon may also use self-retaining sutures to position and support tissue where there is no wound in procedures such as cosmetic surgery of the face, neck, abdominal or thoracic region among others.
More specifically, self-retaining sutures can be used in superficial and deep surgical procedures in humans and animals for closing wounds, repairing traumatic injuries or defects, joining tissues together [bringing severed tissues into approximation, closing an anatomical space, affixing single or multiple tissue layers together, creating anastomoses between two hollow (luminal) structures, adjoining tissues, attaching or reattaching tissues to their proper anatomical location], attaching foreign elements to tissues (affixing medical implants, devices, prostheses and other functional or supportive devices), and for repositioning tissues to new anatomical locations (repairs, tissue elevations, tissue grafting and related procedures) to name but a few examples.
Sutures typically consist of a filamentous suture thread attached to a needle with a sharp point (attachment of sutures and surgical needles is described in U.S. Pat. Nos. 3,981,307, 5,084,063, 5,102,418, 5,123,911, 5,500,991, 5,722,991, 6,012,216, and 6,163,948, and U.S. Patent Application Publication No. U.S. 2004/0088003). Classically, the needle is advanced through the desired tissue on one side of the wound and then through the adjacent side of the wound to form a “loop” which is then completed by tying a knot in the suture.
Sutures materials are broadly classified as being degradable or bioabsorbable (i.e., they break down completely in the body over time), such as those composed of catgut, glycolic acid polymers and copolymers, lactic acid polymers and copolymers, and polyether-esters based copolymers such as polyglycolide or lactide copolymers with polyglycols or polyethers; or as being non-absorbable (permanent; nondegradable), such as those made of polyamide, polytetrafluoroethylene, polyethylene terephthalate, polyurethane, polyether-esters based copolymers such as polybutylene or polyethylene terephthalate with polyglycols or polyethers, metal alloys, metal (e.g., stainless steel wire), polypropylene, polyethelene, silk, and cotton. Degradable (bioabsorbable) sutures have been found to be particularly useful in situations where suture removal might jeopardize the repair or where the natural healing process renders the support provided by the suture material unnecessary after wound healing has been completed; as in, for example, completing an uncomplicated skin closure. Nondegradable (non-absorbable) sutures are used in wounds where healing may be expected to be protracted or where the suture material is needed to provide physical support to the wound for long periods of time; as in, for example, deep tissue repairs, high tension wounds, many orthopedic repairs and some types of surgical anastomoses.
Bioabsorbable sutures can be made of materials which are broken down in tissue after a given period of time, which depending on the material can be from ten days to eight weeks. The sutures are used therefore in many of the internal tissues of the body. In most cases, three weeks is sufficient for the wound to close firmly. At that time the suture is not needed any more, and the fact that it disappears is an advantage, as there is no foreign material left inside the body and no need for the patient to have the sutures removed. In rare cases, bioabsorbable sutures can cause inflammation and be rejected by the body rather than absorbed. Bioabsorbable sutures were first made from the intestines of mammals. For example, gut sutures can be made of specially prepared bovine or ovine intestine, and can be untreated (plain catgut), tanned with chromium salts to increase the suture persistence in the body (chromic catgut), or heat-treated to give more rapid absorption (fast catgut). Concern about transmitting diseases such as bovine spongiform encephalopathy, has resulted in the gut being harvested from stock which have been tested to determine that the natural polymers used as suture materials do not carry viral diseases. Bioabsorbable sutures can be made of synthetic polymer fibers, which can be monofilaments or braided.
Self-retaining sutures are designed for engaging tissue when the suture is pulled in a direction other than that in which it was originally deployed in the tissue. Knotless tissue-approximating devices having barbs have been previously described in, for example, U.S. Pat. No. 5,374,268, disclosing armed anchors having barb-like projections, while suture assemblies having barbed lateral members have been described in U.S. Pat. Nos. 5,584,859 and 6,264,675. One of the earlier patents describing a self-retaining suture is U.S. Pat. No. 3,716,058, which discloses a suture having one or more relatively rigid barbs at its opposite ends; the presence of the barbs just at the ends of the suture would limit the barbs' effectiveness. Sutures having a plurality of barbs positioned along a greater portion of the suture are described in U.S. Pat. No. 5,931,855, which discloses a unidirectional self-retaining suture, and U.S. Pat. No. 6,241,747, which discloses a bidirectional self-retaining suture. Methods and apparatus for forming barbs on sutures by cutting barbs into a suture body have been described in, for example, U.S. Pat. Nos. 6,848,152 and 7,225,512. Methods of manufacturing sutures with frusto-conical retainers have also been described, for example, in European Patent 1 075 843 and U.S. Patent Publication No. 2007/0038429.
Despite the advantages of existing self-retaining sutures, there still remains a need and desire for new and preferably improved self-retaining sutures, and methods of making the same. For example, retainers formed by cutting into a suture body have a tendency to sometimes lie flat, i.e., not stand up or fan out as desired. Additionally, many existing techniques (e.g., cutting techniques) for manufacturing self-retaining sutures result in retainers having elevation angles that are less than desired.